Neurostimulation systems are devices that generate electrical pulses and deliver the pulses to nerve tissue to treat a variety of disorders. Spinal cord stimulation (SCS) is the most common type of neurostimulation. In SCS, electrical pulses are delivered to nerve tissue in the spine typically for the purpose of chronic pain control. Applying electrical energy to the spinal cord associated with regions of the body afflicted with chronic pain can induce “paresthesia” (a subjective sensation of numbness or tingling) in the afflicted bodily regions which can effectively mask the transmission of non-acute pain sensations to the brain.
Neurostimulation systems generally include a pulse generator and one or more leads. The pulse generator is typically implemented using a metallic housing that encloses circuitry for generating the electrical pulses, control circuitry, communication circuitry, a rechargeable battery, etc. The pulse generating circuitry is coupled to one or more stimulation leads through electrical connections provided in a “header” of the pulse generator.
Each stimulation lead includes a lead body of insulative material that encloses wire conductors. The distal end of the stimulation lead includes multiple electrodes that are electrically coupled to the wire conductors. The proximal end of the lead body includes multiple terminals, which are also electrically coupled to the wire conductors, that are adapted to receive electrical pulses. The distal end of a respective stimulation lead is implanted at the location adjacent or within the tissue to be electrically stimulated. The proximal end of the stimulation lead is connected to the header of the pulse generator or to an intermediate “extension” lead.
In certain cases, it is desirable to use a larger number of conductor wires within the lead body to permit the use of a larger number of electrodes. For example, deep brain stimulation leads may employ multiple groups of segmented electrodes disposed axially from the distal tip of the stimulation lead. The segmented electrodes enable greater directional control of the stimulation field. Also, cortical leads and paddle leads may employ larger numbers of electrodes.
Fabrication of lead bodies with larger numbers of conductor wires can be a relatively complex process. In one known fabrication process, a first layer of conductor wires are wound about a mandrel and, then, a second layer of conductor wires are wound about the first layer to form the lead body of the stimulation lead. During the wire winding process, insulative material is provided to embed the conductor wires. Electrode attachment occurs by exposing individual conductor wires by removing insulative material from the lead body. However, exposing an individual conductor wire within the interior layer without exposing any of the other wires can be challenging and time consuming. Accordingly, manufacturing costs can be excessive and manufacturing yields can be less than optimal.